1. Field of the Invention
The present invention relates to a spindle motor.
2. Description of the Related Art
A hard disk drive (HDD), an information storage device, is a device for reading data stored on a disc or writing data to a disc with a read/write head.
A hard disk drive requires a disc driving device for driving a disc, and a small spindle motor is used in the disc driving device.
A spindle motor employs a fluid dynamic bearing assembly (or a hydrodynamic bearing assembly), in which a lubricating fluid is interposed between a shaft, a rotary member of the fluid dynamic bearing assembly, and a sleeve, a fixed member of the fluid dynamic bearing assembly, and the shaft is supported by fluid pressure generated in the lubricating fluid.
Spindle motors are required to have high capacity and to be thinned, and as spindle motors are thinned and reduced in size, bearing rigidity is inevitably weakened.
Bearing rigidity is an important factor determining rotational characteristics of spindle motors, affected by an interval between dynamic pressure generating grooves, i.e., a length of a bearing span.
Namely, as the length of the bearing span is increased, bearing rigidity is increased to enhance rotational characteristics of a motor, and thus, even in the case that a motor has high capacity and is thinned, bearing rigidity may not be affected.
Also, a lubricating fluid injected into a fluid dynamic bearing assembly may be leaked to the outside thereof, or an amount of the lubricating fluid may be reduced due to evaporation, reducing pressure generation in a fluid dynamic bearing and leading to a problem with performance and a life span of the spindle motor.
Thus, research into a spindle motor that may have high capacity and be thin without degrading bearing rigidity, have rigidity sufficient to allow an internal component thereof to resist deformation in spite of external impacts applied thereto, and have performance and life span maximized by securing a storage space of a lubricating fluid is urgently required to be conducted.